A study designed to determine the effect of metformin on free fatty acid metabolism and lipid peroxydation in patients with polycystic ovary syndrome (PCOS) and insulin resistence. PCOS is the most common form of infertility in the United States and effects approximately 6% of all women of reproductive age. Chronic anovulation, hyper- androgenism, and enlarged cystic ovaries are characteristic of this disease. Also, prominant features are insulin resistence and compensatory hyperinsulinemia (excess amount of insulin in the blood), which are thought to play a role in the development of PCOS. Other possible problems are increased hairgrowth, difficulty getting pregnant, higher levels of bad cholesterol, and higher risk of stroke and heart attack at a younger than average age. The department of Obstetrics and Gynecology and the General Clinical Research Center at MCV are conducting this study using metformin to see if it will decrease the blood levels of fatty free acids, thus possibly reducing the risk of cardiovascular disease. Patients will be recruited from the MCV Resident Gynecology Clinic and from the patients of the private practices of faculty members. Only obese women will be studied. At least 20 new patients a month will be seen as well as PCOS patients who return for routine gynecology exams. After a 12 hour fast, patients will enter the CRC for a complete physical examination and a vaginal ultrasound. An IV will be set up for blood sampling which will occur periodically after the patient drinks a sugar solution. Tests will be done for insulin, glucose, kidney function, fatty free acids, and lipid peroxides. The patient will then be put on metformin or a placebo. Neither the patient nor the physician will know if metformin or placebo is taken. After taking the medication for a designated length of time, a second 12 hour fast will take place. The same tests will be readministered as at the beginning of the study.